This invention relates generally to methods and apparatus for the serial transfer of digital data between microprocessors and in particular to methods and apparatus for increasing the speed of such serial transfer.
The ubiquitous microprocessor is finding increasing application in every aspect of modern life. A primary problem involved with the utilization of such microprocessors is the transfer of data to and from these devices. This problem is particularly burdensome as microprocessors become more and more powerful and greater and greater amounts of data are required and generated. Indeed, the applications in which more than one microprocessor is utilized, the amount of data being transferred requires that either expensive parallel methods or slow serial methods of communication be utilized.
A particular application in which this problem is readily apparent involves the utilization of two microprocessors in a small computer system. Generally, such dual microprocessor systems utilize one microprocessor to control a cathode ray tube display system and keyboard while a second microprocessor performs main processor duties. In such applications the systems designer is faced with the alternative of an expensive parallel data bus or a relatively slow asynchronous serial bus which is generally limited, depending upon the communications protocol utilized, to approximately 19.2 kilobaud. This relatively slow data rate results in inordinate delays between processor action and display and is generally not acceptable to systems designers.